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</table></div></td><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="time_get_byname.html" title="cpp/locale/time get byname"><span class="t-lines"><span>time_get_byname</span></span></a></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="time_put_byname.html" title="cpp/locale/time put byname"><span class="t-lines"><span>time_put_byname</span></span></a></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="numpunct_byname.html" title="cpp/locale/numpunct byname"><span class="t-lines"><span>numpunct_byname</span></span></a></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="moneypunct_byname.html" title="cpp/locale/moneypunct byname"><span class="t-lines"><span>moneypunct_byname</span></span></a></div></div></td></tr>
</table></div></td></tr>
<tr class="t-nv-h2"><td colspan="5"> 编码转换平面</td></tr>
<tr class="t-nv-col-table"><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="codecvt_utf8.html" title="cpp/locale/codecvt utf8"><span class="t-lines"><span>codecvt_utf8</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="codecvt_utf16.html" title="cpp/locale/codecvt utf16"><span class="t-lines"><span>codecvt_utf16</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div></div></td></tr>
</table></div></td><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="codecvt_utf8_utf16.html" title="cpp/locale/codecvt utf8 utf16"><span class="t-lines"><span>codecvt_utf8_utf16</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="codecvt_mode.html" title="cpp/locale/codecvt mode"><span class="t-lines"><span>codecvt_mode</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div></div></td></tr>
</table></div></td></tr>
<tr class="t-nv-h2"><td colspan="5"> C 本地环境</td></tr>
<tr class="t-nv-col-table"><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="setlocale.html" title="cpp/locale/setlocale"><span class="t-lines"><span>setlocale</span></span></a></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="localeconv.html" title="cpp/locale/localeconv"><span class="t-lines"><span>localeconv</span></span></a></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="lconv.html" title="cpp/locale/lconv"><span class="t-lines"><span>lconv</span></span></a></div></div></td></tr>
</table></div></td><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="LC_categories.html" title="cpp/locale/LC categories"><span class="t-lines"><span>LC_ALL</span><span>LC_COLLATE</span><span>LC_CTYPE</span><span>LC_MONETARY</span><span>LC_NUMERIC</span><span>LC_TIME</span></span></a></div></div></td></tr>
</table></div></td></tr>
</table></div><div></div></div></div></div><div class="t-navbar-sep"> </div><div class="t-navbar-head"><strong class="selflink"><tt>std::codecvt</tt></strong><div class="t-navbar-menu"><div><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv-h2"><td colspan="5">成员函数</td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="codecvt/codecvt.html" title="cpp/locale/codecvt/codecvt"><span class="t-lines"><span>codecvt::codecvt</span></span></a></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="codecvt/~codecvt.html" title="cpp/locale/codecvt/~codecvt"><span class="t-lines"><span>codecvt::~codecvt</span></span></a></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="codecvt/out.html" title="cpp/locale/codecvt/out"><span class="t-lines"><span>codecvt::out</span><span>codecvt::do_out</span></span></a></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="codecvt/in.html" title="cpp/locale/codecvt/in"><span class="t-lines"><span>codecvt::in</span><span>codecvt::do_in</span></span></a></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="codecvt/unshift.html" title="cpp/locale/codecvt/unshift"><span class="t-lines"><span>codecvt::unshift</span><span>codecvt::do_unshift</span></span></a></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="codecvt/encoding.html" title="cpp/locale/codecvt/encoding"><span class="t-lines"><span>codecvt::encoding</span><span>codecvt::do_encoding</span></span></a></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="codecvt/always_noconv.html" title="cpp/locale/codecvt/always noconv"><span class="t-lines"><span>codecvt::always_noconv</span><span>codecvt::do_always_noconv</span></span></a></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="codecvt/length.html" title="cpp/locale/codecvt/length"><span class="t-lines"><span>codecvt::length</span><span>codecvt::do_length</span></span></a></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="codecvt/max_length.html" title="cpp/locale/codecvt/max length"><span class="t-lines"><span>codecvt::max_length</span><span>codecvt::do_max_length</span></span></a></div></div></td></tr>
</table></div><div></div></div></div></div><div class="t-navbar-sep"> </div></div>
<table class="t-dcl-begin"><tbody>
<tr class="t-dsc-header">
<td> <div>定义于头文件 <code><a href="../header/locale.html" title="cpp/header/locale">&lt;locale&gt;</a></code>
 </div></td>
<td></td>
<td></td>
</tr>
<tr class="t-dcl">
<td class="t-dcl-nopad"> <div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1">&lt;</span> <br>
<p>    <span class="kw1">class</span> InternT, <br>
    <span class="kw1">class</span> ExternT, <br>
    <span class="kw1">class</span> State<br>
</p>
<span class="sy1">&gt;</span> <span class="kw1">class</span> codecvt<span class="sy4">;</span></span></div></td>
<td class="t-dcl-nopad">  </td>
<td class="t-dcl-nopad">  </td>
</tr>
<tr class="t-dcl-sep"><td></td><td></td><td></td></tr>
</tbody></table>
<p>类模板 <code>std::codecvt</code> 封装字符串的转换，包括宽和多字节，从一种编码到另一种。通过 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="../io/basic_fstream.html"><span class="kw1720">std::<span class="me2">basic_fstream</span></span></a><span class="sy1">&lt;</span>CharT<span class="sy1">&gt;</span></span></span> 进行的所有 I/O 操作都使用流中感染的 <span class="t-c"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">codecvt</span><span class="sy1">&lt;</span>CharT, <span class="kw4">char</span>, <a href="../string/multibyte/mbstate_t.html"><span class="kw1179">std::<span class="me2">mbstate_t</span></span></a><span class="sy1">&gt;</span></span></span> 本地环境平面。
</p>
<div class="t-inheritance-diagram">
<div class="center"><div class="noresize" style="height: 88px; width: 306px; "><map name="ImageMap_1_1421689534"><area href="codecvt_base.html" shape="rect" coords="5,4,107,36" alt="cpp/locale/codecvt base" title="cpp/locale/codecvt base"><area href="locale/facet.html" shape="rect" coords="5,52,107,85" alt="cpp/locale/locale/facet" title="cpp/locale/locale/facet"></map><img alt="std-codecvt-inheritance.svg" src="../../../common/images/f/f1/std-codecvt-inheritance.svg" width="306" height="88" usemap="#ImageMap_1_1421689534"></div></div>
<div style="text-align:center;">
<p><span style="font-size:0.7em; line-height:130%">继承图</span>
</p>
</div>
</div>
<p>标准库提供以下独立（本地环境无关）特化：
</p>
<table class="t-dsc-begin">

<tr class="t-dsc-header">
<td colspan="2"> <div>定义于头文件 <code>&lt;locale&gt;</code> </div>
</td></tr>

<tr class="t-dsc">
<td>  <span class="t-c"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">codecvt</span><span class="sy1">&lt;</span><span class="kw4">char</span>, <span class="kw4">char</span>, <a href="../string/multibyte/mbstate_t.html"><span class="kw1179">std::<span class="me2">mbstate_t</span></span></a><span class="sy1">&gt;</span></span></span>
</td>
<td> 恒等转换
</td></tr>

<tr class="t-dsc">
<td>  <span class="t-c"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">codecvt</span><span class="sy1">&lt;</span><span class="kw4">char16_t</span>, <span class="kw4">char</span>, <a href="../string/multibyte/mbstate_t.html"><span class="kw1179">std::<span class="me2">mbstate_t</span></span></a><span class="sy1">&gt;</span></span></span>
</td>
<td> 在 UTF-16 和 UTF-8 间转换 <span class="t-mark-rev t-since-cxx11">(C++11 起)</span><span class="t-mark-rev t-deprecated-cxx20">(C++20 中弃用)</span>
</td></tr>

<tr class="t-dsc">
<td>  <span class="t-c"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">codecvt</span><span class="sy1">&lt;</span><span class="kw4">char16_t</span>, char8_t, <a href="../string/multibyte/mbstate_t.html"><span class="kw1179">std::<span class="me2">mbstate_t</span></span></a><span class="sy1">&gt;</span></span></span>
</td>
<td> 在 UTF-16 和 UTF-8 间转换 <span class="t-mark-rev t-since-cxx20">(C++20 起)</span>
</td></tr>

<tr class="t-dsc">
<td>  <span class="t-c"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">codecvt</span><span class="sy1">&lt;</span><span class="kw4">char32_t</span>, <span class="kw4">char</span>, <a href="../string/multibyte/mbstate_t.html"><span class="kw1179">std::<span class="me2">mbstate_t</span></span></a><span class="sy1">&gt;</span></span></span>
</td>
<td> 在 UTF-32 和 UTF-8 间转换 <span class="t-mark-rev t-since-cxx11">(C++11 起)</span><span class="t-mark-rev t-deprecated-cxx20">(C++20 中弃用)</span>
</td></tr>

<tr class="t-dsc">
<td>  <span class="t-c"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">codecvt</span><span class="sy1">&lt;</span><span class="kw4">char32_t</span>, char8_t, <a href="../string/multibyte/mbstate_t.html"><span class="kw1179">std::<span class="me2">mbstate_t</span></span></a><span class="sy1">&gt;</span></span></span>
</td>
<td> 在 UTF-32 和 UTF-8 间转换 <span class="t-mark-rev t-since-cxx20">(C++20 起)</span>
</td></tr>

<tr class="t-dsc">
<td>  <span class="t-c"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">codecvt</span><span class="sy1">&lt;</span><span class="kw4">wchar_t</span>, <span class="kw4">char</span>, <a href="../string/multibyte/mbstate_t.html"><span class="kw1179">std::<span class="me2">mbstate_t</span></span></a><span class="sy1">&gt;</span></span></span>
</td>
<td> 在系统原生宽和单字节窄字符集间转换
</td></tr>
</table>
<p>另外， C++ 程序中构造每个的 locale 对象实装上述特化其自身的（本地环境特定）版本。
</p>
<h3><span class="mw-headline" id=".E6.88.90.E5.91.98.E7.B1.BB.E5.9E.8B">成员类型</span></h3>
<table class="t-dsc-begin">

<tr class="t-dsc-sep">
<td colspan="2">  
</td></tr>
<tr class="t-dsc-hitem">
<td> 成员类型
</td>
<td> 定义
</td></tr>


<tr class="t-dsc">
<td>  <code>intern_type</code>
</td>
<td>  <code>InternT</code>
</td></tr>

<tr class="t-dsc">
<td>  <code>extern_type</code>
</td>
<td>  <code>ExternT</code>
</td></tr>

<tr class="t-dsc">
<td>  <code>state_type</code>
</td>
<td>  <code>State</code>
</td></tr>
</table>
<h3><span class="mw-headline" id=".E6.88.90.E5.91.98.E5.87.BD.E6.95.B0">成员函数</span></h3>
<table class="t-dsc-begin">

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div t-dsc-member-nobold-div"><div><a href="codecvt/codecvt.html" title="cpp/locale/codecvt/codecvt"> <span class="t-lines"><span>(构造函数)</span></span></a></div></div>
</td>
<td>  构造新的 codecvt 平面 <br> <span class="t-mark">(公开成员函数)</span>
</td></tr>

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div t-dsc-member-nobold-div"><div><a href="codecvt/~codecvt.html" title="cpp/locale/codecvt/~codecvt"> <span class="t-lines"><span>(析构函数)</span></span></a></div></div>
</td>
<td>  销毁 codecvt 平面 <br> <span class="t-mark">(受保护成员函数)</span>
</td></tr>

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="codecvt/out.html" title="cpp/locale/codecvt/out"> <span class="t-lines"><span>out</span></span></a></div></div>
</td>
<td>  调用 <code>do_out</code>  <br> <span class="t-mark">(公开成员函数)</span> </td></tr>

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="codecvt/in.html" title="cpp/locale/codecvt/in"> <span class="t-lines"><span>in</span></span></a></div></div>
</td>
<td>  调用 <code>do_in</code> <br> <span class="t-mark">(公开成员函数)</span> </td></tr>

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="codecvt/unshift.html" title="cpp/locale/codecvt/unshift"> <span class="t-lines"><span>unshift</span></span></a></div></div>
</td>
<td>  调用 <code>do_unshift</code>  <br> <span class="t-mark">(公开成员函数)</span> </td></tr>

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="codecvt/encoding.html" title="cpp/locale/codecvt/encoding"> <span class="t-lines"><span>encoding</span></span></a></div></div>
</td>
<td>  调用 <code>do_encoding</code> <br> <span class="t-mark">(公开成员函数)</span> </td></tr>

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="codecvt/always_noconv.html" title="cpp/locale/codecvt/always noconv"> <span class="t-lines"><span>always_noconv</span></span></a></div></div>
</td>
<td>  调用 <code>do_always_noconv</code>  <br> <span class="t-mark">(公开成员函数)</span> </td></tr>

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="codecvt/length.html" title="cpp/locale/codecvt/length"> <span class="t-lines"><span>length</span></span></a></div></div>
</td>
<td>  调用 <code>do_length</code>  <br> <span class="t-mark">(公开成员函数)</span> </td></tr>

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="codecvt/max_length.html" title="cpp/locale/codecvt/max length"> <span class="t-lines"><span>max_length</span></span></a></div></div>
</td>
<td>  调用 <code>do_max_length</code>  <br> <span class="t-mark">(公开成员函数)</span> </td></tr>
</table>
<h3><span class="mw-headline" id=".E6.88.90.E5.91.98.E5.AF.B9.E8.B1.A1">成员对象</span></h3>
<table class="t-dsc-begin">

<tr class="t-dsc-sep">
<td colspan="2">  
</td></tr>
<tr class="t-dsc-hitem">
<td> 成员名
</td>
<td> 类型
</td></tr>


<tr class="t-dsc">
<td>  <code>id</code> <span class="t-cmark">[静态]</span>
</td>
<td>  <span class="t-lc"><a href="locale/id.html" title="cpp/locale/locale/id">std::locale::id</a></span>
</td></tr>
</table>
<h3><span class="mw-headline" id=".E5.8F.97.E4.BF.9D.E6.8A.A4.E6.88.90.E5.91.98.E5.87.BD.E6.95.B0">受保护成员函数</span></h3>
<table class="t-dsc-begin">

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="codecvt/out.html" title="cpp/locale/codecvt/out"> <span class="t-lines"><span>do_out</span></span></a></div><div><span class="t-lines"><span><span class="t-cmark">[虚]</span></span></span></div></div>
</td>
<td>  从 internT 转换字符串为 externT 转换字符串，如在写入文件时 <br> <span class="t-mark">(虚受保护成员函数)</span> </td></tr>

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="codecvt/in.html" title="cpp/locale/codecvt/in"> <span class="t-lines"><span>do_in</span></span></a></div><div><span class="t-lines"><span><span class="t-cmark">[虚]</span></span></span></div></div>
</td>
<td>  从 externT 转换字符串为 internT ，如在从文件读取时 <br> <span class="t-mark">(虚受保护成员函数)</span> </td></tr>

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="codecvt/unshift.html" title="cpp/locale/codecvt/unshift"> <span class="t-lines"><span>do_unshift</span></span></a></div><div><span class="t-lines"><span><span class="t-cmark">[虚]</span></span></span></div></div>
</td>
<td>  为不完整转换生成 externT 字符的终止字符序列 <br> <span class="t-mark">(虚受保护成员函数)</span> </td></tr>

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="codecvt/encoding.html" title="cpp/locale/codecvt/encoding"> <span class="t-lines"><span>do_encoding</span></span></a></div><div><span class="t-lines"><span><span class="t-cmark">[虚]</span></span></span></div></div>
</td>
<td>  返回产生一个 internT 字符所需的 externT 字符数，若此值为常数 <br> <span class="t-mark">(虚受保护成员函数)</span> </td></tr>

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="codecvt/always_noconv.html" title="cpp/locale/codecvt/always noconv"> <span class="t-lines"><span>do_always_noconv</span></span></a></div><div><span class="t-lines"><span><span class="t-cmark">[虚]</span></span></span></div></div>
</td>
<td>  测试平面编码是否对所有合法值为恒等转换 <br> <span class="t-mark">(虚受保护成员函数)</span> </td></tr>

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="codecvt/length.html" title="cpp/locale/codecvt/length"> <span class="t-lines"><span>do_length</span></span></a></div><div><span class="t-lines"><span><span class="t-cmark">[虚]</span></span></span></div></div>
</td>
<td>  计算转换成给定的 internT 缓冲区会消耗的 externT 字符串长度 <br> <span class="t-mark">(虚受保护成员函数)</span> </td></tr>

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="codecvt/max_length.html" title="cpp/locale/codecvt/max length"> <span class="t-lines"><span>do_max_length</span></span></a></div><div><span class="t-lines"><span><span class="t-cmark">[虚]</span></span></span></div></div>
</td>
<td>  返回能转换成单个 internT 字符的最大 externT 字符数 <br> <span class="t-mark">(虚受保护成员函数)</span> </td></tr>
</table>
<div class="t-inherited">
<h2> <span class="mw-headline" id=".E7.BB.A7.E6.89.BF.E8.87.AA_std::codecvt_base">继承自  <a href="codecvt_base.html" title="cpp/locale/codecvt base"> <span style="font-size:0.7em; line-height:130%">std::</span>codecvt_base</a> </span></h2>
<table class="t-dsc-begin">

<tr class="t-dsc-sep">
<td colspan="2">  
</td></tr>
<tr class="t-dsc-hitem">
<td> 成员类型
</td>
<td> 定义
</td></tr>


<tr class="t-dsc">
<td>  <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">enum</span> result <span class="br0">{</span> ok, partial, error, noconv <span class="br0">}</span><span class="sy4">;</span></span></span>
</td>
<td> 无作用域枚举类型
</td></tr>
</table>
<table class="t-dsc-begin">

<tr class="t-dsc-sep">
<td colspan="2">  
</td></tr>
<tr class="t-dsc-hitem">
<td> 枚举常量
</td>
<td> 定义
</td></tr>


<tr class="t-dsc">
<td>  <code>ok</code>
</td>
<td> 完成转换而无错误
</td></tr>

<tr class="t-dsc">
<td>  <code>partial</code>
</td>
<td> 未转换所有源字符
</td></tr>

<tr class="t-dsc">
<td>  <code>error</code>
</td>
<td> 遇到非法字符
</td></tr>

<tr class="t-dsc">
<td>  <code>noconv</code>
</td>
<td> 不要求转换，输入与输出类型相同
</td></tr>
</table>
</div>
<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">示例</span></h3>
<div class="t-example"><p>下例示例用在 codecvt&lt;wchar_t, char, mbstate_t&gt; 实现 UTF-8 转换的本地环境读取 UTF-8 环境，并用 std::codecvt 的标准特化转换 UTF-8 字符串为 UTF-16</p><div class="t-example-live-link"><div class="coliru-btn coliru-btn-run-init">运行此代码</div></div>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="co2">#include &lt;iostream&gt;</span>
<span class="co2">#include &lt;fstream&gt;</span>
<span class="co2">#include &lt;string&gt;</span>
<span class="co2">#include &lt;locale&gt;</span>
<span class="co2">#include &lt;iomanip&gt;</span>
<span class="co2">#include &lt;codecvt&gt;</span>
 
<span class="co1">// 工具包装器，用于为 wstring/wbuffer 适配绑定到 locale 的平面</span>
<span class="kw1">template</span><span class="sy1">&lt;</span><span class="kw1">class</span> Facet<span class="sy1">&gt;</span>
<span class="kw1">struct</span> deletable_facet <span class="sy4">:</span> Facet
<span class="br0">{</span>
    <span class="kw1">template</span><span class="sy1">&lt;</span><span class="kw1">class</span> ...<span class="me1">Args</span><span class="sy1">&gt;</span>
    deletable_facet<span class="br0">(</span>Args<span class="sy3">&amp;&amp;</span> ...<span class="me1">args</span><span class="br0">)</span> <span class="sy4">:</span> Facet<span class="br0">(</span><a href="../utility/forward.html"><span class="kw1117">std::<span class="me2">forward</span></span></a><span class="sy1">&lt;</span>Args<span class="sy1">&gt;</span><span class="br0">(</span>args<span class="br0">)</span>...<span class="br0">)</span> <span class="br0">{</span><span class="br0">}</span>
    ~deletable_facet<span class="br0">(</span><span class="br0">)</span> <span class="br0">{</span><span class="br0">}</span>
<span class="br0">}</span><span class="sy4">;</span>
 
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
<span class="br0">{</span>
    <span class="co1">// UTF-8 窄多字节编码</span>
    <a href="../string/basic_string.html"><span class="kw1230">std::<span class="me2">string</span></span></a> data <span class="sy1">=</span> <span class="kw1">reinterpret_cast</span><span class="sy1">&lt;</span><span class="kw4">const</span> <span class="kw4">char</span><span class="sy2">*</span><span class="sy1">&gt;</span><span class="br0">(</span><span class="sy2">+</span>u8<span class="st0">"z<span class="es3">\u00df</span><span class="es3">\u6c34</span><span class="es4">\U0001f34c</span>"</span><span class="br0">)</span><span class="sy4">;</span>
                       <span class="co1">// 或 reinterpret_cast&lt;const char*&gt;(+u8"zß水🍌")</span>
                       <span class="co1">// 或 "\x7a\xc3\x9f\xe6\xb0\xb4\xf0\x9f\x8d\x8c"</span>
 
    <a href="../io/basic_ofstream.html"><span class="kw1733">std::<span class="me2">ofstream</span></span></a><span class="br0">(</span><span class="st0">"text.txt"</span><span class="br0">)</span> <span class="sy1">&lt;&lt;</span> data<span class="sy4">;</span>
 
    <span class="co1">// 使用系统提供的本地环境的 codecvt 平面</span>
    <a href="../io/basic_ifstream.html"><span class="kw1746">std::<span class="me2">wifstream</span></span></a> fin<span class="br0">(</span><span class="st0">"text.txt"</span><span class="br0">)</span><span class="sy4">;</span>
    <span class="co1">// 从 wifstream 的读取将使用 codecvt&lt;wchar_t, char, mbstate_t&gt;</span>
    <span class="co1">// 此 locale 的 codecvt 从 UTF-8 转换到 UCS4 （在如 Linux 的系统上）</span>
    fin.<span class="me1">imbue</span><span class="br0">(</span><a href="locale.html"><span class="kw1894">std::<span class="me2">locale</span></span></a><span class="br0">(</span><span class="st0">"en_US.UTF-8"</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
    <a href="../io/cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="st0">"The UTF-8 file contains the following UCS4 code points: <span class="es1">\n</span>"</span><span class="sy4">;</span>
    <span class="kw1">for</span> <span class="br0">(</span><span class="kw4">wchar_t</span> c<span class="sy4">;</span> fin <span class="sy1">&gt;&gt;</span> c<span class="sy4">;</span> <span class="br0">)</span>
        <a href="../io/cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="st0">"U+"</span> <span class="sy1">&lt;&lt;</span> <a href="../io/manip/hex.html"><span class="kw1782">std::<span class="me2">hex</span></span></a> <span class="sy1">&lt;&lt;</span> <a href="../io/manip/setw.html"><span class="kw1797">std::<span class="me2">setw</span></span></a><span class="br0">(</span><span class="nu0">4</span><span class="br0">)</span> <span class="sy1">&lt;&lt;</span> <a href="../io/manip/setfill.html"><span class="kw1795">std::<span class="me2">setfill</span></span></a><span class="br0">(</span><span class="st0">'0'</span><span class="br0">)</span> <span class="sy1">&lt;&lt;</span> c <span class="sy1">&lt;&lt;</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
 
    <span class="co1">// 使用标准（本地环境无关） codecvt 平面</span>
    <a href="wstring_convert.html"><span class="kw1899">std::<span class="me2">wstring_convert</span></span></a><span class="sy1">&lt;</span>
        deletable_facet<span class="sy1">&lt;</span>std<span class="sy4">::</span><span class="me2">codecvt</span><span class="sy1">&lt;</span><span class="kw4">char16_t</span>, <span class="kw4">char</span>, <a href="../string/multibyte/mbstate_t.html"><span class="kw1179">std::<span class="me2">mbstate_t</span></span></a><span class="sy1">&gt;&gt;</span>, <span class="kw4">char16_t</span><span class="sy1">&gt;</span> conv16<span class="sy4">;</span>
    <a href="../string/basic_string.html"><span class="kw1234">std::<span class="me2">u16string</span></span></a> str16 <span class="sy1">=</span> conv16.<span class="me1">from_bytes</span><span class="br0">(</span>data<span class="br0">)</span><span class="sy4">;</span>
 
    <a href="../io/cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="st0">"The UTF-8 file contains the following UTF-16 code points: <span class="es1">\n</span>"</span><span class="sy4">;</span>
    <span class="kw1">for</span> <span class="br0">(</span><span class="kw4">char16_t</span> c <span class="sy4">:</span> str16<span class="br0">)</span>
        <a href="../io/cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="st0">"U+"</span> <span class="sy1">&lt;&lt;</span> <a href="../io/manip/hex.html"><span class="kw1782">std::<span class="me2">hex</span></span></a> <span class="sy1">&lt;&lt;</span> <a href="../io/manip/setw.html"><span class="kw1797">std::<span class="me2">setw</span></span></a><span class="br0">(</span><span class="nu0">4</span><span class="br0">)</span> <span class="sy1">&lt;&lt;</span> <a href="../io/manip/setfill.html"><span class="kw1795">std::<span class="me2">setfill</span></span></a><span class="br0">(</span><span class="st0">'0'</span><span class="br0">)</span> <span class="sy1">&lt;&lt;</span> c <span class="sy1">&lt;&lt;</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
<span class="br0">}</span></pre></div></div>
<p>输出：
</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="text source-text"><pre class="de1">The UTF-8 file contains the following UCS4 code points:
U+007a
U+00df
U+6c34
U+1f34c
The UTF-8 file contains the following UTF-16 code points:
U+007a
U+00df
U+6c34
U+d83c
U+df4c</pre></div></div> 
</div>
<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">参阅</span></h3>
<table class="wikitable" style="font-size:85%; text-align:center;">

<tr>
<th> 字符转换
</th>
<th> 本地环境定义多字节<br>(UTF-8, GB18030)
</th>
<th> UTF-8<br>
</th>
<th> UTF-16<br>
</th></tr>
<tr>
<th> UTF-16
</th>
<td style="background: #90ff90; color: black; vertical-align: middle; text-align: center;" class="table-yes"><a href="../string/multibyte/mbrtoc16.html" title="cpp/string/multibyte/mbrtoc16"><tt>mbrtoc16</tt></a> / <a href="../string/multibyte/c16rtomb.html" title="cpp/string/multibyte/c16rtomb"><tt>c16rtomb</tt></a><span class="t-mark">(有 C11 的 DR488)</span>
</td>
<td style="background: #90ff90; color: black; vertical-align: middle; text-align: center;" class="table-yes"><strong class="selflink"><tt>codecvt</tt></strong>&lt;char16_t, char, mbstate_t&gt;<br><a href="codecvt_utf8_utf16.html" title="cpp/locale/codecvt utf8 utf16"><tt>codecvt_utf8_utf16</tt></a>&lt;char16_t&gt;<br><a href="codecvt_utf8_utf16.html" title="cpp/locale/codecvt utf8 utf16"><tt>codecvt_utf8_utf16</tt></a>&lt;char32_t&gt;<br><a href="codecvt_utf8_utf16.html" title="cpp/locale/codecvt utf8 utf16"><tt>codecvt_utf8_utf16</tt></a>&lt;wchar_t&gt;
</td>
<td style="background: #ececec; color: grey; vertical-align: middle; text-align: center;" class="table-na"> <small>N/A</small>
</td></tr>
<tr>
<th> UCS2
</th>
<td style="background: #90ff90; color: black; vertical-align: middle; text-align: center;" class="table-yes"><a href="../string/multibyte/c16rtomb.html" title="cpp/string/multibyte/c16rtomb"><tt>c16rtomb</tt></a><span class="t-mark">(无 C11 的 DR488)</span>
</td>
<td style="background: #90ff90; color: black; vertical-align: middle; text-align: center;" class="table-yes"><a href="codecvt_utf8.html" title="cpp/locale/codecvt utf8"><tt>codecvt_utf8</tt></a>&lt;char16_t&gt;<br>
<p><a href="codecvt_utf8.html" title="cpp/locale/codecvt utf8"><tt>codecvt_utf8</tt></a>&lt;wchar_t&gt;<span class="t-mark">(Windows)</span>
</p>
</td>
<td style="background: #90ff90; color: black; vertical-align: middle; text-align: center;" class="table-yes"><a href="codecvt_utf16.html" title="cpp/locale/codecvt utf16"><tt>codecvt_utf16</tt></a>&lt;char16_t&gt;<br>
<p><a href="codecvt_utf16.html" title="cpp/locale/codecvt utf16"><tt>codecvt_utf16</tt></a>&lt;wchar_t&gt;<span class="t-mark">(Windows)</span>
</p>
</td></tr>
<tr>
<th> UTF-32
</th>
<td style="background: #90ff90; color: black; vertical-align: middle; text-align: center;" class="table-yes">
<p><a href="../string/multibyte/mbrtoc32.html" title="cpp/string/multibyte/mbrtoc32"><tt>mbrtoc32</tt></a> / <a href="../string/multibyte/c32rtomb.html" title="cpp/string/multibyte/c32rtomb"><tt>c32rtomb</tt></a>
</p>
</td>
<td style="background: #90ff90; color: black; vertical-align: middle; text-align: center;" class="table-yes">
<p><strong class="selflink"><tt>codecvt</tt></strong>&lt;char32_t, char, mbstate_t&gt;<br>
<a href="codecvt_utf8.html" title="cpp/locale/codecvt utf8"><tt>codecvt_utf8</tt></a>&lt;char32_t&gt;<br>
<a href="codecvt_utf8.html" title="cpp/locale/codecvt utf8"><tt>codecvt_utf8</tt></a>&lt;wchar_t&gt;<span class="t-mark">(非 Windows)</span>
</p>
</td>
<td style="background: #90ff90; color: black; vertical-align: middle; text-align: center;" class="table-yes">
<p><a href="codecvt_utf16.html" title="cpp/locale/codecvt utf16"><tt>codecvt_utf16</tt></a>&lt;char32_t&gt;<br>
<a href="codecvt_utf16.html" title="cpp/locale/codecvt utf16"><tt>codecvt_utf16</tt></a>&lt;wchar_t&gt;<span class="t-mark">(非 Windows)</span>
</p>
</td></tr>
<tr>
<th> 系统宽<br>UTF-32<span class="t-mark">(非 Windows)</span><br>UCS2<span class="t-mark">(Windows)</span>
</th>
<td style="background: #90ff90; color: black; vertical-align: middle; text-align: center;" class="table-yes">
<p><a href="../string/multibyte/mbsrtowcs.html" title="cpp/string/multibyte/mbsrtowcs"><tt>mbsrtowcs</tt></a> / <a href="../string/multibyte/wcsrtombs.html" title="cpp/string/multibyte/wcsrtombs"><tt>wcsrtombs</tt></a><br>
<a href="use_facet.html" title="cpp/locale/use facet"><tt>use_facet</tt></a>&lt;<strong class="selflink"><tt>codecvt</tt></strong><br>
&lt;wchar_t, char, mbstate_t&gt;&gt;(<a href="locale.html" title="cpp/locale/locale"><tt>locale</tt></a>)
</p>
</td>
<td style="background:#ff9090; color:black; vertical-align: middle; text-align: center;" class="table-no"> 无
</td>
<td style="background:#ff9090; color:black; vertical-align: middle; text-align: center;" class="table-no"> 无
</td></tr></table>
<table class="t-dsc-begin">

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="codecvt_base.html" title="cpp/locale/codecvt base"> <span class="t-lines"><span>codecvt_base</span></span></a></div></div>
</td>
<td>  定义字符转换错误 <br> <span class="t-mark">(类模板)</span>
</td></tr>

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="codecvt_byname.html" title="cpp/locale/codecvt byname"> <span class="t-lines"><span>codecvt_byname</span></span></a></div></div>
</td>
<td>  为具名本地环境构造 codecvt 平面 <br> <span class="t-mark">(类模板)</span>
</td></tr>

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="codecvt_utf8.html" title="cpp/locale/codecvt utf8"> <span class="t-lines"><span>codecvt_utf8</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span><span><span class="t-mark-rev t-deprecated-cxx17">(C++17 中弃用)</span></span></span></div></div>
</td>
<td>  在 UTF-8 与 UCS2/UCS4 间转换 <br> <span class="t-mark">(类模板)</span> </td></tr>

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="codecvt_utf16.html" title="cpp/locale/codecvt utf16"> <span class="t-lines"><span>codecvt_utf16</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span><span><span class="t-mark-rev t-deprecated-cxx17">(C++17 中弃用)</span></span></span></div></div>
</td>
<td>  在 UTF-16 与 UCS2/UCS4 间转换 <br> <span class="t-mark">(类模板)</span> </td></tr>

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="codecvt_utf8_utf16.html" title="cpp/locale/codecvt utf8 utf16"> <span class="t-lines"><span>codecvt_utf8_utf16</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span><span><span class="t-mark-rev t-deprecated-cxx17">(C++17 中弃用)</span></span></span></div></div>
</td>
<td>  在 UTF-8 与 UTF-16 间转换 <br> <span class="t-mark">(类模板)</span> </td></tr>
</table>

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